Currently, some disposable absorbent articles such as diapers, sanitary napkins, and pantiliners are provided with a low density airfelt absorbent core. Airfelt, or comminuted wood pulp, is typically made in a process that involves several steps. The first step is one in which pulp fibers are suspended in water and introduced to a moving screen from the headbox in a wetlaid paper process. The water is removed by a combination of gravity and vacuum before introduction to a drying process to form a relatively high basis weight material that is referred to as “drylap”. Drylap may be in sheet or roll form. Thereafter, the drylap is shipped to the absorbent article manufacturer. The absorbent article manufacturer subjects the drylap to comminution process or shredding to make airfelt or “fluff” via an airlaid process. This is typically done on-line in an absorbent article manufacturing line.
Airfelt has several limitations when used as an absorbent core material in disposable absorbent articles. Airfelt typically has low integrity, and is subject to bunching and roping when wet. Airfelt typically has a low density and cannot provide as much capillary work potential as a higher density material. In addition, airfelt has the same density throughout the thickness, and is not readily formed into structures having zones or layers with higher densities.
Airlaid structures are another type of absorbent material commonly used in absorbent articles. The air laying process involves the comminution or shredding of drylap to make airfelt or “fluff”. Binder materials, such as latex binder, may then be added to provide strength and integrity to the material. Super-absorbent polymers are often added in the air laying process as well. Airlaid structures can be formed in a manner which does provide zones with higher densities, as in US 2003/0204178 A1, but this involves more expensive processes and materials. The air laying process is often done at an intermediate supplier, resulting in added cost for shipping the material to the converting operation. The combination of more costly materials, processing, and shipping results in a significantly more expensive material and a more complex supply chain.
Various different absorbent structures and other structures used in absorbent articles, and methods of making the same, are disclosed in the patent literature, including: U.S. Pat. No. 3,017,304, Burgeni; U.S. Pat. No. 3,509,007, Kalwaites; U.S. Pat. No. 4,189,344, Busker; U.S. Pat. No. 4,992,324, Dube; U.S. Pat. No. 5,143,679, Weber; U.S. Pat. No. 5,242,435, Murji; U.S. Pat. No. 5,518,801, Chappell, et al.; U.S. Pat. No. 5,562,645, Tanzer, et al.; U.S. Pat. No. 5,634,915, Osterhahl; U.S. Pat. No. 5,743,999, Kamps; U.S. Pat. No. 6,344,111 B1, Wilhelm; U.S. Patent Application Publication No. 2003/0204178 A1, Febo, et al.; U.S. Patent Application Publication No. 2006/0151914, Gerndt; U.S. Patent Application Publication No. 2008/0217809 A1, Zhao, et al.; U.S. Patent Application Publication No. 2008/0221538 A1, Zhao, et al.; U.S. Patent Application Publication No. 2008/0221539 A1, Zhao, et al.; U.S. Patent Application Publication No. 2008/0221541 A1, Lavash, et al.; U.S. Patent Application Publication No. 2008/0221542 A1, Zhao, et al.; U.S. Patent Application Publication No. 2010/0318047 A1, Ducker, et al.; and, EP 0 598 970 B2. However, the search for improved absorbent structures and methods of making the same has continued.
It is desirable to provide improved absorbent members and methods of making the same. In particular, it is desirable to provide absorbent members with improved liquid acquisition, flexibility, tensile strength, and fluid retention. Ideally, it is desirable to produce such improved absorbent members at a low cost.